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Monday, September 9, 2013

Soybean Rust Update

Sept 5, 2013

From David Holshouser, Extension
Agronomist

and Hillary Mehl, Extension Plant
Pathologist

Virginia Tech – Tidewater AREC

Asian soybean rust
was confirmed earlier today in Scotland County, NC. Scotland County is on
the NC/SC border (see map below). There were sporulating pustules on 5 of
50 leaves examined. No soybean rust was found on leaf samples taken from
Lenoir County, which is closer to Virginia. This puts soybean rust approximately
140 miles from South Hill, 160 miles from Emporia, and 190 miles from
Suffolk.

In general, we will only
recommend a fungicide spray if soybean rust has been confirmed within 100 miles
of our soybean fields. Therefore, there is no need to apply fungicide
for control of soybean rust in Virginia at this time. Applying
fungicide too early will only reduce its effectiveness once the disease
arrives. Furthermore, soybean yield will not be affected if rust infects
the crop after the R6 development stage (seed touching each other in the pod);
therefore, fungicides are not recommended after the R6 stage, even if soybean
rust is found close by.

Although soybean rust
is not close enough to Virginia to initiate fungicide sprays at this time, the
disease has moved faster than previous years. Most of our full-season
(May-planted soybean) have reached the R6 stage (full-seed); therefore, these
soybean are “safe” from any yield loss that may result from soybean rust
infestation. However, much of our double-cropped soybean are still
susceptible; they are anywhere from the R3 (early pod) to R5 (late pod)
development stages. We will continue to monitor soybean rust movement
across NC, continue to check soybean fields in Virginia, and let everyone know
immediately if soybean rust is found in or close to Virginia.

For more details on Asian
soybean rust and its movement, see the following website:

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